Monday, April 9, 2007

A report issued Friday from the UN-sponsored Intergovernmental Panel on Climate Change (IPCC) has once again prompted debate about how to respond to global warming. Perhaps one of the biggest obstacles to meaningful progress on this issue comes from the perception that changing our consumption levels will drastically reduce our standard of living. This kind of hysteria is fueled by the commonly quoted phrase: "if everyone consumed like North Americans, we'd need five planets to support us". But if you consider the natural resources, population, and consumption patterns of the U.S. by itself, how unsustainable are we, really?

This is similar to the question raised by popular "ecological footprint" calculators, but it takes into account the fact that our nation has more natural resources and a lower population density than most of the rest of the world. So in a sense, it's more fair. Basically, "sustainability" is a careful balance of three factors: (1) the available natural resources, often lumped into a quantity called "biocapacity", (2) the average consumption level of those natural resources, known as our "footprint", and (3) the total size of the population. Since total biocapacity is fairly constant, any increase in population erodes the available footprint per person. So if we want to maintain a certain standard of living, we need to either control population growth or decrease our footprint over time.

As you can imagine, the average footprint in the U.S. is actually growing slowly over time, mostly from energy use (the inability of the environment to absorb all of the carbon dioxide we release). The last time we were in balance with the available resources was around 1969. As it stands today, the average footprint is about twice the available biocapacity per person. So we only need two planets to be sustainable as a nation, not five. The reason is simple: it's harder for Africa to be locally sustainable because they don't have enough arable land, and it's harder for China because they have too many people. We should certainly help them address these problems, but those challenges are distinct from the challenge of sustainability at home.

Even so, the average footprint in the U.S. is still twice as high as it needs to be if we want to live a sustainable lifestyle. So you might ask: when in history was the standard of living in the U.S. half of what it is today? Even if you use a traditional economic measure of the standard of living, like "real GDP per capita" (which is adjusted for inflation and population growth), you find that to be sustainable we would need to adopt the lifestyle of the mid-1960's. That doesn't seem like such a sacrifice, and it's close to the "1969" balance mentioned above because improvements in (agricultural and energy) efficiency have basically made up for all of the population growth since then.

The average U.S. footprint is currently about 24 acres, while the locally sustainable level is around 12. Something to shoot for.